Gobo

A gobo is an object placed inside or in front of a light source to control the shape of the emitted light and its shadow. For studio photography purposes, the term "gobo" refers to any device that casts a shadow and various pieces of equipment that go in front of a light (such as a gobo arm or gobo head). In theatrical lighting, however, the term more specifically refers to a device placed in "the gate" or at the "point of focus" between the light source, called a lamp, and the lenses (or other optics). The exact derivation of the term gobo is unclear, although it appears to have originated in cinema studios in the 1930s. It may be an American slang abbreviation of "go-between", or "go-before" (just as New York's "SoHo" signifies the area "South of Houston Street"). Some lighting professionals believe that it is an acronym for "goes before optics" or, less often, "goes between optics."